US20040085630A1 - Bidirectional use of a telescope for a free space optical communication system - Google Patents

Bidirectional use of a telescope for a free space optical communication system Download PDF

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Publication number
US20040085630A1
US20040085630A1 US10/695,769 US69576903A US2004085630A1 US 20040085630 A1 US20040085630 A1 US 20040085630A1 US 69576903 A US69576903 A US 69576903A US 2004085630 A1 US2004085630 A1 US 2004085630A1
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US
United States
Prior art keywords
optical surface
transmitting
telescope
receiving
axis
Prior art date
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Abandoned
Application number
US10/695,769
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English (en)
Inventor
Elena Grassi
Giovanni Paoli
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Alcatel Lucent SAS
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Alcatel SA
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Filing date
Publication date
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Assigned to ALCATEL reassignment ALCATEL ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: GASSI, ELENA, PAOLI, GIOVANNI
Publication of US20040085630A1 publication Critical patent/US20040085630A1/en
Abandoned legal-status Critical Current

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B23/00—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices
    • G02B23/02—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices involving prisms or mirrors
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B17/00—Systems with reflecting surfaces, with or without refracting elements
    • G02B17/02—Catoptric systems, e.g. image erecting and reversing system
    • G02B17/06—Catoptric systems, e.g. image erecting and reversing system using mirrors only, i.e. having only one curved mirror
    • G02B17/0605—Catoptric systems, e.g. image erecting and reversing system using mirrors only, i.e. having only one curved mirror using two curved mirrors
    • G02B17/061—Catoptric systems, e.g. image erecting and reversing system using mirrors only, i.e. having only one curved mirror using two curved mirrors on-axis systems with at least one of the mirrors having a central aperture
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B17/00—Systems with reflecting surfaces, with or without refracting elements
    • G02B17/02—Catoptric systems, e.g. image erecting and reversing system
    • G02B17/06—Catoptric systems, e.g. image erecting and reversing system using mirrors only, i.e. having only one curved mirror
    • G02B17/0605—Catoptric systems, e.g. image erecting and reversing system using mirrors only, i.e. having only one curved mirror using two curved mirrors
    • G02B17/0615—Catoptric systems, e.g. image erecting and reversing system using mirrors only, i.e. having only one curved mirror using two curved mirrors off-axis or unobscured systems in wich all of the mirrors share a common axis of rotational symmetry

Definitions

  • the present invention pertains generally to electronic communications systems. More specifically, the present invention relates to communication systems which transmit and receive information signals that are carried by analog or digital modulation of laser light beams (Free Space Optical communication), including the case of multiple wavelength transmission (DWDM). Still more in particular, the present invention relates to a bi-directional use of a telescope in a transceiver for a bi-directional free space optics system.
  • DWDM multiple wavelength transmission
  • the free space optics (briefly, FSO) telecommunication systems are known for transmitting a light signal through the air.
  • the operation of such optical systems transmitting a modulated light signal is basically based on one or more lasers coupled to one or more lens (transmission side) and one or more lens for focusing the received laser beam on the detecting area of the receiver (receiver side).
  • a free space optical system used for carrying telecommunication information can take many advantages by using the same optical device both for the transmitting and the receiving paths.
  • combination of the transmitting and the receiving paths can be done also by using two different wavelengths for the two directions and performing the beam-splitting of the full bi-directional path by means of dicroic filters or the like.
  • the dicroic filter must be different (e.g., long pass and short pass inverted) or with different mounting (e.g.: different mechanical positioning of the Tx and Rx devices).
  • this solution reduces drastically the transmission and receiving losses.
  • losses are reduced by 25%, due to the fact that half of the diameter of the main mirror is used for transmission, whereas the Tx losses due to the secondary mirror obstruction can be of the order of 15%.
  • the main object of the present invention is providing a telescope for a free space optical communication system operable in a bi-directional manner and keeping at a minimum the additional optical path losses.
  • a further object of the present invention is providing a bi-directional telescope for a free space optical communication system avoiding the shadow of secondary mirror inside the transmitted beam.
  • a still further object of the present invention is providing a bi-directional telescope for a free space optical communication system avoiding the use of different wavelengths between the two direction of the optical path.
  • each terminal includes an optical surface (telescope) used both for the transmitting and the receiving path. This is obtained by using a minor part the optical surface for transmission, leaving the major surface to the reception. Furthermore, according to the invention, the surface exploited for transmitting is off-axis.
  • FIG. 1 shows a schematic side view of a first embodiment of bi-directional telescope for a free space optics telecommunication system according to the present invention
  • FIG. 2 shows a schematic front view thereof
  • FIG. 3 shows a schematic side view of a second embodiment of bi-directional telescope for a free space optics telecommunication system according to the present invention
  • FIG. 4 shows a schematic front view thereof
  • FIG. 5 shows a schematic side view of a third embodiment of bi-directional telescope for a free space optics telecommunication system according to the present invention.
  • FIG. 6 shows a schematic front view thereof.
  • the present invention could be implemented in several different ways according to the various optical schemes.
  • the idea according to the present invention can be applied to all known optical schemes but because the problem of the shadow in the transmitted beam is relevant to most of reflective schemes, only arrangements that does not result in a shadowed transmitted beam will be shown and described as preferred embodiments.
  • FIGS. 1 - 4 show two preferred embodiments of the present invention.
  • FIGS. 1 and 2 show a true Cassegrain optical scheme.
  • FIG. 1 shows a schematic side view of a first embodiment of bi-directional telescope for a free space optics telecommunication system according to the present invention.
  • the telescope 10 of FIG. 1 comprises an optical transmitting device 12 , an optical receiving device 14 , a primary mirror 16 and a secondary mirror 18 . Both the optical transmitting device 12 and the optical receiving device 14 could be laser diodes or optical fibers.
  • Primary mirror 16 is parabolic and secondary mirror 18 is hyperbolic.
  • the primary mirror 16 is provided with a hole 20 concentric with the primary mirror 16 . Also the secondary mirror is provided with an hole 22 .
  • the optical receiver device (diode or fiber) 14 is located in the focus of the whole configuration (primary mirror and secondary mirror).
  • the transmitter device (laser or fiber) 12 is located at the focus of the primary mirror 16 , and it transmits through the hole 22 in the secondary mirror 18 .
  • the area that becomes illuminated by the transmitter device is 24 .
  • the axis 12 ′ of the emission device 12 shall be orthogonal to the surface of the primary mirror 16 in the center of the illuminated area 24 .
  • the transmitted beam will be off the center of the primary mirror 16 , but parallel to the axis 14 ′ of the receiver configuration.
  • the primary mirror hole 20 can be more than twice. In this case, it will be possible to avoid any additional optic to obtain the collimation of the transmit beam.
  • a beam expander (not shown) at the source 12 , to give the correct divergence of the beam to be matched with the aperture of the relevant optical scheme, should be used.
  • FIGS. 1 and 2 works also with others reflective optical configurations that use parabolic primary mirror surface, for example the Newton reflector optical scheme.
  • laser light emitted by transmitting device 12 forms a transmitting beam (indicated by a dual line) impinging against the reflective surface of primary mirror 16 at the illuminated area 24 ; a TX path is thus formed in a direction parallel to the telescope axis 14 ′ (see reference sign “TX PATH”).
  • the received laser light (indicated by hatched lines and by the reference sign “RX PATH”) that is reflected by the whole reflecting surface 26 of primary mirror 16 , excluding transmitting area 24 , is focused by secondary mirror 18 towards the optical receiving device 14 , passing through the hole 20 .
  • the whole area 26 of primary mirror 16 is used for receiving a light beam carrying a signal while only area 24 (which is minor in comparison with area 26 ) is used for transmitting a laser signal through the air.
  • FIG. 3 a further preferred embodiment of the present invention is shown.
  • the same or similar reference numbers have been used for indicating the same or functionally equivalent parts.
  • the arrangement of FIGS. 3 and 4 is advantageous with respect to the one of FIGS. 1 and 2 as there is no need to make a hole in the secondary mirror 18 .
  • the man skilled in the art will realize that such a second embodiment provides the same illuminated area 24 as in the previous arrangement.
  • the light emitting device 12 is placed behind the primary mirror 16 and the transmitting beam is deflected by a 90° prism (or mirror) 30 .
  • this second solution is applicable to all possible optical configurations (even refractive or catadioptric) and requires an off-axis prism (or flat mirror) 30 . Possibly, it further requires a beam expander at the source 12 to give the right divergence of the beam to be matched to the aperture of the relevant optical scheme.
  • FIGS. 5 and 6 show a possible implementation of a bi-directional telescope according to the present invention when it is used with two transmitting devices 121 and 122 .
  • two holes 221 and 222 are provided in the secondary mirror 18 for letting the two transmitting beams (see TX 1 PATH and TX 2 PATH) to pass through the secondary mirror itself.
  • the two transmitting beams form two corresponding illuminated areas 241 , 242 on the surface of the primary mirror 16 .
  • proper focusing lenses at each of the multiple transmitters 121 , 122 may be inserted for exploiting small surface for each transmitter. Through such an arrangement, it will be still possible to maintain the overall losses below a desired value.
  • the above described second embodiment can be easily implemented with two (or more) transmitters by providing two or more corresponding off-axis prisms (or flat mirrors) 30 .
  • the solution according to the present invention uses the smaller area of the main collecting surface for the transmission and leaves the largest area for the reception, further exploiting the concept of off-axis optic transmission.
  • the main advantage is to keep at the minimum the additional optical path losses (to less than 1.0 dB, Tx+Rx) and, at the same time, to avoid the shadow of secondary mirror inside the transmitted beam. It also avoids the needs to use of different wavelength between the two directions of the path.
  • the present invention relates to a bi-directional telescope for a laser on air telecommunication system.
  • the telescope comprises: a primary optical surface (for instance, a mirror or lens 16 ); at least one transmitting device 12 ; 121 , 122 forming at least one transmitting beam impinging against the primary optical surface 16 at an at least one illuminated area 24 ; 241 , 242 , the at least one transmitting beam having a corresponding axis 12 ′; 121 ′, 122 ′; and a receiving device 14 collecting the power deflected by an optical surface 26 of the primary optical surface 16 into a receiving beam, the receiving beam having an axis 14 ′.
  • the telescope is characterized in that the optical surface 26 of the primary optical surface 16 is larger than the at least one illuminated area 24 ; 241 , 242 and in that the transmitting beam axis 12 ′; 121 ′, 122 ′ does not coincide with the receiving beam axis 14 ′.
  • the telescope according to the present invention comprises a secondary optical surface (for instance, a mirror or lens 18 ), wherein the received power deflected by the optical surface 26 of the primary optical device 16 is focused by the secondary optical surface into the receiving beam.
  • a secondary optical surface for instance, a mirror or lens 18
  • the present invention also relates to a method for transmitting and receiving optical signals through the air by a single bi-directional telescope.
  • the method comprises the steps of: providing a primary optical surface; providing at least one transmitting device forming at least one transmitting beam impinging against the primary mirror at an at least one illuminated area, the at least one transmitting beam having a corresponding axis; and providing a receiving device collecting the power deflected by an optical surface of the primary optical surface into a receiving beam, the receiving beam having an axis.
  • the method is characterized in that the optical surface is larger than the at least one illuminated area and in that the transmitting beam axis does not coincide with the receiving beam axis.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Astronomy & Astrophysics (AREA)
  • Optical Communication System (AREA)
  • Lenses (AREA)
  • Telescopes (AREA)
US10/695,769 2002-10-31 2003-10-30 Bidirectional use of a telescope for a free space optical communication system Abandoned US20040085630A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP02292718.0 2002-10-31
EP02292718A EP1416307A1 (de) 2002-10-31 2002-10-31 Bidirektionales Teleskop

Publications (1)

Publication Number Publication Date
US20040085630A1 true US20040085630A1 (en) 2004-05-06

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US10/695,769 Abandoned US20040085630A1 (en) 2002-10-31 2003-10-30 Bidirectional use of a telescope for a free space optical communication system

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EP (1) EP1416307A1 (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20160271186A1 (en) * 2010-08-19 2016-09-22 The Regents Of The University Of California Compositions comprising perivascular stem cells and nell-1 protein
RU2603820C1 (ru) * 2015-09-29 2016-11-27 Публичное акционерное общество "Красногорский завод им. С.А. Зверева" Телескоп
CN110941075A (zh) * 2019-11-28 2020-03-31 中国科学院微电子研究所 反射式光学系统及其装调测试方法
US11409099B2 (en) 2020-02-25 2022-08-09 Honeywell Limited Honeywell Limitée Optical apparatus
US11409089B2 (en) 2020-02-25 2022-08-09 Honeywell Limited Honeywell Limitée Optical apparatus

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7366419B2 (en) * 2004-11-22 2008-04-29 Northrop Grumman Corporation Spatial transmit/receive isolation method for optical communication systems
DE102006018743A1 (de) * 2006-04-22 2007-10-25 Carl Zeiss Optronics Gmbh Teleskop zur optischen Freiraumtelekommunikation
FR2940472B1 (fr) * 2008-12-24 2011-03-18 Commissariat Energie Atomique Couplage optique entre un collecteur optique de telescope et un recepteur

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3371212A (en) * 1963-11-13 1968-02-27 Barnes Eng Co Light spot projection system for infrared camera
US3781552A (en) * 1972-08-02 1973-12-25 K Kadrmas Self-calibrating multiple field of view telescope for remote atmospheric electromagnetic probing and data acquisition
US4777660A (en) * 1984-11-06 1988-10-11 Optelecom Incorporated Retroreflective optical communication system

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4439012A (en) * 1982-01-11 1984-03-27 The United States Of America As Represented By The Secretary Of The Army Dual-secondary mirror cassegrain optical system
US4695139A (en) * 1984-12-26 1987-09-22 Hughes Aircraft Company Plural-zone mirror focusing system
RU2042165C1 (ru) * 1992-05-21 1995-08-20 Научно-производственное объединение "Государственный институт прикладной оптики" Зеркальная телескопическая насадка для лазерного приемно-передающего устройства
RU2042163C1 (ru) * 1992-07-06 1995-08-20 Научно-производственное объединение "Государственный институт прикладной оптики" Зеркальная телескопическая насадка для лазерного приемно-передающего устройства
US5390040A (en) * 1994-02-04 1995-02-14 Martin Marietta Corporation Optical transceiver for free-space communication links
US6462846B1 (en) * 1998-07-29 2002-10-08 Trw Inc. Shared telescope optical communication terminal

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3371212A (en) * 1963-11-13 1968-02-27 Barnes Eng Co Light spot projection system for infrared camera
US3781552A (en) * 1972-08-02 1973-12-25 K Kadrmas Self-calibrating multiple field of view telescope for remote atmospheric electromagnetic probing and data acquisition
US4777660A (en) * 1984-11-06 1988-10-11 Optelecom Incorporated Retroreflective optical communication system

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20160271186A1 (en) * 2010-08-19 2016-09-22 The Regents Of The University Of California Compositions comprising perivascular stem cells and nell-1 protein
RU2603820C1 (ru) * 2015-09-29 2016-11-27 Публичное акционерное общество "Красногорский завод им. С.А. Зверева" Телескоп
CN110941075A (zh) * 2019-11-28 2020-03-31 中国科学院微电子研究所 反射式光学系统及其装调测试方法
US11409099B2 (en) 2020-02-25 2022-08-09 Honeywell Limited Honeywell Limitée Optical apparatus
US11409089B2 (en) 2020-02-25 2022-08-09 Honeywell Limited Honeywell Limitée Optical apparatus

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Publication number Publication date
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Owner name: ALCATEL, FRANCE

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:GASSI, ELENA;PAOLI, GIOVANNI;REEL/FRAME:015464/0706

Effective date: 20030909

STCB Information on status: application discontinuation

Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION